Proper form is essential for effective and safe results when performing resistive exercises such as with weight machines used for strength training. This is especially true for exercise of the muscle groups found in the torso during spinal extention and spinal flexion exercises, as it is known in the art. This exercise motion focuses on training the lower back muscles, the abdominals, and obliques. Too often however, the various machines and devices available for this purpose lack proper features to ensure that users execute a safe and effective motion thereupon to exercise the back or abdominal muscles.
Many torso exercise machines use a conventional cable and pulley system coupled to a weight stack. A user typically sits on a stationary surface, and then applies his or her upper body against another surface. A user may then apply force on this latter surface whilst rotating the torso about the base of the spine, to either: (a) flex the spine by contracting the abdominal muscles so as to train the abdominal muscles group, or (b) extend the spine by contracting the back muscles so as to train the muscles of the central and lower back. To achieve this range of motion, a user's hips are often unsecured, and may be free to move or shift while the exercise is performed. This allows other skeletal motions such as hip flexion to substitute for spinal flexion and conversely hip extension to substitute for spinal extention. When that is allowed to happen, the user will be exercising the hip and not the abdominals and back musculature. Some torso exercise machines may use a back support to try to limit the extent of spinal extention range especially in the lumbar region of the spine but unless there is some significant force holding the back against this back support, they are traditionally ineffective at stabilizing the pelvis and preventing hip flexion/extention substitution.
It is desirable therefore, to provide a weight training machine which allows a user to exercise his or her muscles in the torso region, while sufficiently stabilizing the pelvis to effectively block hip motion and substitution and focus the training effect on the intended muscles of the abdomen and lower back.